This invention relates generally to a machine for handling parts and more specifically relates to a parts handling machine of the same general type as disclosed in Dixon U.S. Pat. No. 4,002,247. In that machine, a gripping mechanism having a pair of opposing jaws is mounted on a carriage and is adapted to be shifted horizontally and vertically to pick a part out of a track and to transfer the part to a different position.
The carriage of the machine disclosed in the Dixon patent is guided for back and forth movement by slots or cam tracks which are formed in a main support plate. Rollers are mounted on the carriage and ride within the tracks. When the carriage is arranged to move horizontally and vertically, each track is shaped substantially as an inverted L and includes a generally horizontal portion and a generally vertical portion. As the carriage moves back and forth, each roller rides around the corner between the horizontal and vertical portions of the track.
Difficulty has been encountered in keeping the rollers positioned tightly within the tracks while leaving the rollers free to roll without skidding. If the rollers are not held tightly within the tracks, the rollers are free to shift radially and thus impair the smoothness and the positioning accuracy of the gripping mechanism. On the other hand, a roller which is closely confined by the track tends to roll along both sides of the track and tends to skid, particularly when the roller moves around the corner of the track.